The goals of the proposed work are: 1) development of interleukin-3 (IL-3) dependent cell lines from normal mouse marrow cells to be used to study the molecular events occurring during IL-3 dependent cellular proliferation; 2) comparison of the effect of hemopoietic growth factors on the factor-dependent cell lines and purified populations of hemopoietic progenitor cells. These studies will concentrate on post-ligand receptor events that occur in response to growth factors or hormones that induce differentiation; 3) correlation between cellular proto-oncogene expression, production of second messengers, and responsiveness to leukemic cell inducing agents of factor-dependent cell lines; 4) examination of the responsiveness of immortal factor-dependent and factor-independent cell lines to prostaglandin E and the role of the GTP-binding protein that stimulates adenylate cyclase (Gs) in this phenomenon; and 5) murine myeloid leukemic cell lines whose proliferation is dependent on added hemopoietic growth factors will be transfected with cloned genes for IL-3 or GM-CSF. The mode of expression of the newly transfected genes will be studied to further define the potential role of autocrine regulatory mechanisms in leukemogenesis.